Big thanks to Gilthresa for putting these together, and allowing me along for the ride!
Crushing Bones and Cracking Skulls
There are two strategies that make this easily obtainable, the first is to simply have your tank pick up all the elementals and when the boss starts to cast this ability they use a cooldown to get through the incoming damage, the next is to simply have someone that can snare or stun them do so as soon as the chains have been broken, they adds should still be in range of the boss and die. Repeat until you have killed 10 then defeat the boss.
I found only one way to obtain this achievement easily and that was by releasing the adds one by one, simply engage the boss and have two of your group members block two of the beams (making sure to watch their stacks) and leave the third open, let the add evolve and DPS it down fast, make sure to interrupt the ability Shadow strike, this causes massive damage to your tank and could cause a wipe, after the first is dead let your healer replenish some mana and simply release another, repeat until all three are dead then kill the boss.
Too Hot to Handle
This achievement will just come from doing the boss normally, basically you want to drag the boss through the fire when it has about 7-8 seconds on the debuff only letting him gain 1-2 stacks at a time, slowly let this build up to 15 stacks and then kill him.
This achievement is earned by not getting more than four stacks of Crepuscular veil, simply have someone kite the 3 adds and you should have no issue getting this as long as they didn’t get within melee range long enough to gain four stacks.